There are many situations where excessive ice build-up is disadvantageous. One of the major difficulties is the force required to break up the ice. The prevention of ice formation as for example by lowering the freezing point is frequently impractical. However, if the strength of the ice was reduced, its break-up would be much easier making the accumulation less onerous.
When the surface moisture on particulate solids freezes the ice acts as a powerful adhesive holding the particles together in a mass. The adhesivity is influenced by both the particle size of the solids and the moisture content as shown later. For example, coal with as little as 4 percent moisture will, when frozen, cohere so strongly as to require special handling to break up the frozen mass. It thus becomes difficult to unload or dump railway cars, trucks and other conveyances used to transport coal, mineral ores and other finely divided solids. It also makes difficult the movement of coal out of outdoor coal storage piles in a condition for fuel or other use. Unloading frozen coal from railroad cars is time consuming, can result in blocked dump chutes and can often leave as much as 30 to 60 tons of coal in the car. Various techniques such as vibration, steam lances, fires under the cars, infrared heating in warming sheds and even dynamiting have been tried to unload frozen cars. The safety problems inherent in some of these techniques are obvious. Others are ineffective or totally impractical from an economic standpoint, particularly where conditions are so severe as to cause entire carloads of coal to freeze solid (as distinguished from merely perimeter freezing). All of these factors point to the definite need of developing an economic method of treating coal, ores and other divided solids to overcome the problems of transport of those solids.
Various approaches have been used with limited degrees of success. Sodium chloride and calcium chloride salts have been added to moist coal as it is being loaded with some degree of success toward reducing the freezing problem. However, such salts contribute to the corrosion of all equipment with which the solids come in contact and are detrimental to the coking process when used with coking coal. Oil has been used to freeze-proof coal with questionable effectiveness. Oil soluble surfactants have been added to the oil but with questionable results. Ethylene glycol has been employed, but although successful, the cost of treatment has been very high.